Proposal of mapping between TIME concepts of numerical weather simulations and ISO/DIS 19156 Observations and Measurements (O&M 2.0)

This page just make a summary of the Proposal made in the Bonn TC by Jeremy Tandy

Following comments from members of the DWG, the specification of the 'assimilationWindow' concept has been updated. A new version (2.3) of Jeremy's presentation can be found here:


This proposal is base on ISO/DIS 19156 Observations and Measurements ... also known as O&M 2.0

Met Ocean Time Concept O&M Modelling Comments or examples

1-phenomenonTime: period covered by the forecast; the time domain of the forecast result phenomenonTime

The attribute phenomenonTime:TM_Object shall describe the time that the result ( applies to the property of the feature-of-interest ( This is often the time of interaction by a sampling procedure (8.1.3) or observation procedure ( with a real-world feature.

NOTE 1 The phenomenonTime is the temporal parameter normally used in geospatial analysis of the result.

NOTE 2 If the observedProperty of an observation is ‘occurrence time’ then the result should be the same as the phenomenonTime

For instance if a numerical weather simulation starts at 2010-05-06T00:00Z and the simulation describes the future weather conditions over the subsequent 84 hour period until 2010-05-09T12:00Z,



________ ________ ________
2-resultTime: time at which the last part of the numerical forecast run is made available = When the complete result are published resultTime

The attribute resultTime:TM_Instant shall describe the time when the result became available, typically when the procedure ( associated with the observation was completed For some observations this is identical to the phenomenonTime. However, there are important cases where they differ.

In the example above if the simulation completes at 04:30Z,


________ ________ ________ validTime

If present, the attributevalidTime:TM_Period shall describe the time period during which the result is intended to be used.

NOTE This attribute is commonly required in forecasting applications.

Although the terminology is similar, O&M validTime describes legal or practical usage constraints that are applied to the observation result. For example, validTime would be used with entities such as Terminal Aerodrome Forecasts (TAFs) which are (legally) only valid for 12-hrs (or 18-hrs) after publication. validTime is different to the validity time which is used to describe an instant of interest within the result of the simulation.

For forecast modelling it can be optional. It is not specified here.

________ ________ ________

3-analysisTime: Analysis Time describes the time instant for the initial conditions of a numerical weather simulation.

The analysis Time is chosen from a time-instant toward the middle of the assimilation window where the model state is considered to be more realistic. parameter

If present, the attributes parameter:NamedValue shall describe an arbitrary event-specific parameter. This might be an environmental parameter, an instrument setting or input, or an event-specific sampling parameter that is not tightly bound to either the feature-of-interest ( or to the observation procedure ( To avoid ambiguity, there shall be no more than one parameter with the same name. shall be "analysisTime" for this concept

parameter.value shall be of TYPE time instant"analysisTime" parameter.value=2010-05-06T00:00Z

________ ________ ________
4 assimilationWindow: time period from which observations are selected to be assimilated into the analysis parameter (see above) shall be "assimilationWindow" for this concept

parameter.value shall be of TYPE time period

(note that 'value' can be of any type - for implementation choose TM_Period)

For a simulation with an assimilation window from 21:00 to 02:30 ...




-- MarieFrancoiseVoidrotMartinez - 04 Apr 2011

-- JeremyTandy - 05 Apr 2011
I Attachment Action Size Date Who Comment
OGC_Met-Ocean_DWGIts-about-time2011-03-22_TANDY_v2.3.pdfpdf OGC_Met-Ocean_DWGIts-about-time2011-03-22_TANDY_v2.3.pdf manage 4 MB 05 Apr 2011 - 07:45 JeremyTandy Update of the proposal from Jeremy Tandy discussing how TIME concepts of numerical weather simulations (i.e. forecasts) can be mapped to ISO/DIS 19156 Observations and Measurements
Topic revision: r3 - 05 Apr 2011, MarieFrancoiseVoidrotMartinez
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